I never knew a rocket leaf could speak. Then Meredith Young came along and now I do – although what it has to say is rather sad. Rocket leaves; thinly sliced portobello mushrooms; artfully wilted spinach: these aren't the usual subjects of ­psychologist Young. But, with a team of researchers, she spent days in ­unobtrusive observation of almost 470 undergraduates eating at the canteens of McMaster University in Ontario. They found that when women sat with men they ate rabbit food or other meals "of significantly lower caloric value" than in all-women groups. The more men dining with a woman, the less she ate. Why?

Young women use their food to send a signal to men, suggests the study. Just like clothing accessories, they pick meals to enhance their desirability to the ­opposite sex. "The salad leaves are meant to say, 'I'm pretty; I'm attractive; I take care of myself'," says Young.

And the pressure increases with the number of potential partners around. As for the men, they didn't watch what they scoffed at all.

In arriving at their hypothesis, the researchers made some reasonable ­assumptions: that the undergraduates (largely between 17 and 22 years old) hadn't yet settled down, were in the market for relationships and that the majority were heterosexual. The argument fits with other evidence that our tablemates affect what we eat (close friends tend to push the boat out; strangers are far more uptight), and that others judge us by our food.

When it comes to social perceptions, you really are what you eat. This may explain why few boast of having a Pot Noodle; conversely, salad-eaters come a few forkfuls closer to those connotations of health and attractiveness ­(although I suspect Beyoncé doesn't live on celeriac alone, and that doesn't bother her legions of admirers). And as Young and her researchers note, their female undergraduates appear to ­"believe that men find women who eat less more attractive".

In other words, a young woman may be top of the class in chemical ­engineering, but those Naked Ape-isms still suck her in. As for the diet industry, it's just gained another tagline: rocket leaves – because he's worth it, apparently.